Process for recycling resin scrap and apparatus therefor

ABSTRACT

A process and an apparatus for recycling resin scrap including a thermosetting resin paint film and a thermoplastic resin substrate as its major components, wherein the resin scrap is supplied into a passage of a cylinder, melted, and delivered by delivering means from an upstream side to a downstream side of the passage of the cylinder, and hydrolyzed by a hydrolyzing agent while forming a highly packed region with a resistor. The resistor restricts the resin scrap to flow from the upstream side to the downstream side in a short period of time, and forms the highly packed region where a contact efficiency is enhanced between the resin scrap and the hydrolyzing agent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for recycling resin scrap andan apparatus therefor. In particular, it is applicable to recyclingresin scrap with paint film coated, for instance, recycling vehiclebumpers.

2. Description of the Related Art

It has been required recently to recycle and re-use resin scrap. Whenthe resin scrap comprises thermosetting resin and thermoplastic resin,for instance, when it comprises a thermoplastic resin substrate and athermosetting resin paint film laminated on the substrate, thethermoplastic resin melts, but the thermosetting resin does not melt nordissolve in a solvent. Accordingly, it is difficult to recycle suchresin scrap. This results from the fact that thermosetting resin iscross-linked three-dimensionally therein by thermal setting.

Accordingly, there has been proposed recently a recycling process forthe rein scrap which comprises a thermoplastic resin substrate and athermosetting resin paint film laminated on the substrate. In therecycling process, the resin scrap is Finely pulverized, and the finelypulverized resin scrap is kneaded as it is with a kneader, therebyproducing recycled resin composition. However, by the recycling process,the paint film cannot be fined, and cannot be melted in the kneader. Asa result, the paint film comes to exist as a foreign material in therecycled resin composition. Therefore, molded products made from therecycled resin composition comes to exhibit degraded mechanicalcharacteristics. The degraded mechanical characteristics arise sharplyin impact strength. For example, when vehicle bumpers are made from therecycled resin composition, they exhibit much more deterioratedcollision resistance in cold areas than those made from virgin material.Hence, there arises a problem in that the recycled resin composition canbe used limitedly in minor applications only in which impact strength isnot required.

Hence, the applicants of the present invention developed a new recyclingprocess for producing recycled resin composition which is disclosed inJapanese Re-laid-open Patent Publication No. 5-801,232 based upon a PCTapplication. In the recycling process, resin scrap with a thermosettingresin polyurethane paint film or an amino resin paint film laminated ispulverized, and the pulverized resin scrap is hydrolyzed by heating andmelting under a pressure of 35 kgf/cm² at a temperature of up to 220°C., thereby producing recycled resin composition. By the recyclingprocess, the thermosetting resin constituting the paint film can beeasily converted into low-molecular-weight compounds by the hydrolysiswith the highly heated and pressurized water. After the hydrolysis, thepaint film can be fined into pieces by melting and kneading the resinscrap, and the resulting fined paint film pieces can be dispersed in therecycled resin composition further uniformly. Thus, the paint film donot act as foreign material. Hence, the recycling process canadvantageously give the sufficient mechanical strength to the recycledresin composition. It has been verified by infrared spectroscopy andliquid chromatography that the paint film is converted into thelow-molecular-weight compounds by the hydrolysis.

In addition, as set forth in Japanese Unexamined Patent Publication(KOKAI) No. 5-200,749, another recycling process has been known. In theother recycling process, resin scrap is supplied to a kneader togetherwith a decomposition facilitating agent, such as Lewis acid like tinchloride, alkali metal hydroxide, alkaline-earth metal hydroxide, amineand metal phosphate, it is melted and kneaded at a temperature of 200°C. or more, and thermosetting resin is fined by thermal decomposition soas to disperse in recycled resin composition. According to the recyclingprocess, the decomposition facilitating agent is added in an amount offrom 0.01 to 1% by weight with respect to the resin scrap. Thisrecycling process, however, does not utilize hydrolysis in order torecycle the resin scrap.

SUMMARY OF THE INVENTION

The present invention has been developed as a part of theabove-described new recycling process in which thermosetting resin isconverted into low-molecular-weight compounds by hydrolysis in order toproduce recycled resin composition. It is therefore an object of thepresent invention to provide a process for recycling resin scrap and anapparatus therefor which can reduce time required for recycling andwhich can contribute to highly refining recycled resin composition. Inorder to achieve the object, the present inventors have devised a way ofimproving a contact efficiency between resin material and a hydrolyzingagent in a cylinder, and thereby successfully completed to effectivelycarry out the conversion of the thermosetting resin into thelow-molecular-weight compounds by hydrolysis.

A process for recycling resin scrap and an apparatus therefor accordingto the present invention can accomplish the aforementioned object. In afirst aspect of the present invention, the process uses:

resin material, the resin material comprising scrap includingthermosetting resin and thermoplastic resin as its major components; and

an apparatus having an upstream side and a downstream side, and theapparatus comprising:

a cylinder including a passage, at least part of the passage defining ahydrolysis region; and

means for delivering the resin material from the upstream side to thedownstream side, the delivering means disposed in the passage andincluding a resistor disposed therein so as to restrict the delivery ofthe resin material to the downstream side in the hydrolysis region,thereby forming a highly packed region where a packing efficiency of theresin material is enhanced on an upstream side with respect to theresistor; and

the process comprises the steps of:

melting the thermoplastic resin of the resin material while deliveringthe resin material, having been supplied to the passage of the cylinder,from the upstream side to the downstream side;

hydrolyzing the thermosetting resin by contacting the resin material,undergone the melting step, with a hydrolyzing agent; and

degassing by vaporizing water content resulting from the thermosettingresin undergone the hydrolyzing step;

whereby improving a contact efficiency between the resin material andthe hydrolyzing agent in the hydrolyzing step.

In a second aspect of the present invention, the resin material ishydrolyzed under a pressure of from 10 to 100 kgf/cm² at a temperatureof the resin material from 180° to 280° C., preferably under a pressureof from 20 to 50 kgf/cm² at a temperature of the resin material from200° to 250° C.

In a third aspect of the present invention, the apparatus includes aplurality of the resistors which are disposed at predetermined intervalsin series, and the cylinder which includes a plurality of supply ports,disposed on an upstream side with respect to each of the resistors, forsupplying the hydrolyzing agent to the passage, thereby supplying thehydrolyzing agent to the passage through each of the supply ports.

In a fourth aspect of the present invention, the hydrolyzing agent issupplied in a larger amount to the passage through the supply portswhich are disposed on the upstream side of the passage than through thesupply ports which are disposed on the downstream side of the passage.

In a fifth aspect of the present invention, the hydrolyzing stepincludes a step of selecting water as the hydrolyzing agent, and thewater is added in an amount of from 5 to 40 parts by weight, preferablyin an amount of from 7 to 40 parts by weight, further preferably in anamount of from 7 to 25 parts by weight, with respect to 100 parts byweight of the resin material.

In a sixth aspect of the present invention, the apparatus has anupstream side and a downstream side and comprises:

a cylinder having opposite ends and an intermediate portion, thecylinder including an inlet port for supplying resin material,comprising thermosetting resin and thermoplastic resin, disposed at oneend, an outlet port for discharging recycled resin composition disposedat the other end, a passage connecting the inlet port and the outletport, a supply port for supplying a hydrolyzing agent to the passagedisposed at the intermediate portion, and degassing means disposeddownstream with respect to the supply port; and

delivering means disposed in the passage of the cylinder, and includinga plurality of delivering members, kneading members and resistors;

thereby defining a melting region, a hydrolyzing region, and a degassingregion in the passage of the cylinder in this order from the upstreamside to the downstream side.

In a seventh aspect of the present invention, the resistors areconstituted by at least one member selected from the group consisting ofa sealing ring and a reverse-feed full-flighter, the delivering meansare constituted mainly by a forward-feed full-flighter, and the kneadingmeans are constituted by at least one member selected from the groupconsisting of a forward-feed kneading disk, a reverse-feed kneadingdisk, an orthogonal kneading disk and a gear kneader.

In an eighth aspect of the present invention, crack producing means forproducing cracks in the thermosetting resin of the resin material isfurther disposed on an upstream side with respect to the melting region.

In a ninth aspect of the present invention, washing means for washingthe resin material is further disposed on an upstream side with respectto the melting region.

In a tenth aspect of the present invention, the resistors areconstituted by a rotary member which has an outer peripheral portion,which is disposed in the passage substantially coaxially therewith andwhich has a plurality of grooves lined up in the outer peripheralportion in a circumferential direction, and the hydrolyzing agent supplyport is disposed so as to be capable of facing the grooves.

The hydrolyzing agent employed by the present invention can berepresented by water (e.g., cold water and hot water), and water vapor.Further, it is possible to employ water with alcohol added, and waterwith hydrolysis-facilitating acid and alkali added for the hydrolyzingagent. As for the alcohol, it is possible to utilize hydrophilicalcohol, such as methanol, ethanol, propanol, ethylene glycol, methylcellosolve (Trade Mark), and ethyl cellosolve (Trade Mark). As for theacid, it is possible to employ inorganic acid, such as hydrochloric acidand sulfuric acid, and organic acid, such as acetic acid, oxalic acidand tartaric acid. As for the alkali, it is possible to use inorganicbase, such as sodium hydroxide and potassium hydroxide, and organic basesuch as sodium methoxide. Depending on the types of the resin scrap andthe applications of the recycled product, the hydrolyzing agent isconstituted by appropriately selecting these substances.

The resin scrap used by the present invention includes thermosettingresin and thermoplastic resin as its major components. For instance, athermosetting resin paint film is usually laminated on a thermoplasticresin substrate. As for the paint film, it is possible to employacrylics-melamine resin, alkyd-melamine resin and polyurethane resin.For example, it is possible to employ a paint film which is formed of amajor component, such as alkyd resin, polyester resin and alkyl resin,and a curing agent, such as amino resin (e.g., melamine resin). Thesepaint films are hydrolyzed under highly heated and pressurizedcondition, and their three-dimensionally cross-linked construction isdestroyed, thereby being converted into low-molecular-weight compounds.

As for the thermoplastic resin, any resin can be used as far as it hasthermoplasticity. For instance, it is possible to name polypropylene,polypropylene modified with elastomer, polyethylene, ABS resin, ASresin, polyamide resin, polyester resin, polycarbonate resin andpolyacetal resin for the thermoplastic resin. In addition, it is notpreferable to use resin which is susceptible to the hydrolyzingcondition for the thermoplastic resin.

In the first aspect of the present invention, the resistor is disposedin the delivering means, and restricts the delivery of the resinmaterial to the downstream side in the hydrolysis region, therebyforming a highly packed region where a packing efficiency of the resinmaterial is enhanced on an upstream side with respect to the resistor.As a result, the hydrolyzing agent can be inhibited from going fast tothe downstream side of the cylinder. With this arrangement, thehydrolyzing agent can reside in the hydrolysis region for a prolongedperiod of time, thereby improving a contact efficiency between the resinmaterial and the hydrolyzing agent in the hydrolysis region andfacilitating the hydrolysis of the thermosetting resin.

The resistor can be constituted by a sealing ring, a reverse-feedfull-flighter, or the combinations of a sealing ring and a reverse-feedfull-flighter. The sealing ring seals the passage to reduce a flowpassage area through which the resin material passes. The reverse-feedfull-flighter adjusts the helical direction of screw so as to reverselyfeed the resin material.

In the case where the hydrolysis agent is water, the form of water inthe hydrolysis region depends basically on the pressure and temperaturein the hydrolysis region. Hence, the water can be liquid water, watervapor, or coexistence of the liquid water and the water vapor. Inparticular, when the vapor pressure in the hydrolysis resin is kept atthe saturation vapor pressure or more, the liquid water and the watervapor are believed to coexist.

As having been described so far, in accordance with the first aspect ofthe present invention, there is formed the highly packed region where apacking efficiency of the resin material is enhanced on an upstream sidewith respect to the resistor. Accordingly, the hydrolyzing agent can beinhibited from going fast to the downstream side of the cylinder. As aresult, in the hydrolysis region, the contact efficiency can be improvedbetween the hydrolyzing agent and the resin material, and the hydrolysisof the thermosetting resin can be facilitated. In addition, the highlypacked region also enhances the sealing property. Hence, it is possibleto keep the pressure in the hydrolysis region high, and toadvantageously raise the temperature in the hydrolysis region. Thus, thefirst aspect of the present invention can contribute to reducing therecycling time and highly refining recycled resin composition.Concerning its advantageous effect to recycling apparatus, it can reducethe length of the hydrolysis region in the recycling apparatus, and canadvantageously down-size the recycling apparatus.

In accordance with the second aspect of the present invention, thehydrolysis can be carried out under a pressure of from 10 to 100kgf/cm², and the temperature of the resin material can be raised to atemperature of from 180° to 280° C. Hence, the hydrolysis reaction canbe facilitated, and the length of the hydrolysis region can be reduced.Thus, the second aspect of the present invention can furtheradvantageously down-size the present recycling apparatus.

In accordance with the third aspect of the present invention, aplurality of the resistors are disposed at predetermined intervals inseries in the passage of the cylinder, and the cylinder includes aplurality of supply ports, disposed on an upstream side with respect toeach of the resistors, for supplying the hydrolyzing agent to thepassage. Therefore, the hydrolyzing agent is supplied to the passagethrough each of the supply ports. As a result, the hydrolyzing agent canbe dispersed efficiently in the hydrolysis region to improve theefficiency of the hydrolysis reaction. Thus, the third aspect of thepresent invention can further improve the efficiency of the hydrolysisreaction.

In accordance with the fourth aspect of the present invention, thehydrolyzing agent is supplied in a larger amount to the passage throughthe supply ports which are disposed on the upstream side of the passagethan through the supply ports which are disposed on the downstream sideof the passage. With this arrangement, the resin material placed on theupstream side can be prevented from thermally degrading, though suchresin material is likely to be overheated because of its high viscosityand large shearing friction. Thus, the fourth aspect of the presentinvention can further advantageously refine recycled resin composition.

In accordance with the fifth aspect of the present invention, thehydrolyzing agent is water. The water is added in an amount of from 5 to40 parts by weight with respect to 100 parts by weight of the resinmaterial. It should be noted that the water is supplied more than theamount required for the hydrolysis. Therefore, the resin material can beinhibited from thermally degrading excessively. Thus, the fifth aspectof the present invention can also further advantageously refine recycledresin composition.

The apparatus according to the sixth aspect of the present invention cancarry out the present recycling process.

In accordance with the seventh aspect of the present invention, thereverse-feed full-flighter has a less capability than the forward-feedfull-flighter in terms of the resin material delivery. The sealingexhibits resistance against the resin material delivery. By using thesemembers for the present resistor, it is possible to adjust the residingtime of the resin material in the passage, and to effectively secure thehydrolysis reaction time. In addition, the kneading disks and a gearkneader can produce a highly dispersed state during kneading. By usingthese members for the present resistor, the hydrolyzing agent can behighly dispersed. Thus, the seventh aspect of the present invention caneffectively disperse the hydrolyzing agent in and mix it with the resinmaterial, and accordingly can further satisfactorily carry out thehydrolysis reaction.

In accordance with the eighth aspect of the present invention, since thecrack producing means for producing cracks in the thermosetting resin ofthe resin material is further disposed on an upstream side with respectto the melting region, the thermosetting resin is likely to break intopieces. Therefore, the surface area of the thermosetting resin can beincreased to facilitate the hydrolysis reaction. Thus, the eighth aspectof the present invention can improve the contact efficiency between thehydrolyzing agent and the resin material, and can further advantageouslyrefine recycled resin composition.

In accordance with the ninth aspect of the present invention, since thewashing means for washing the resin material is further disposed on anupstream side with respect to the melting region, the foreign materials,such as dirt and tar, can be separated from the resin material. Hence,the foreign materials can be inhibited from mingling, and simultaneouslythe thermosetting resin is likely to be hydrolyzed. Thus, the ninthaspect of the present invention can further advantageously refinerecycled resin composition.

In accordance with the tenth aspect of the present invention, since theresistors are constituted by a rotary member which has an outerperipheral portion, and which has a plurality of grooves lined up in theouter peripheral portion in a circumferential direction, and since thehydrolyzing agent supplying port is disposed so as to face the grooves,the hydrolyzing agent is spread finely as the rotary member rotates.Therefore, the contact efficiency between the resin material and thehydrolyzing agent can be further improved. Thus, the tenth aspect of thepresent invention can further facilitate the hydrolysis of thethermosetting resin, and can further advantageously refine recycledresin composition.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of itsadvantages will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings and detailedspecification, all of which forms a part of the disclosure:

FIG. 1 is a construction diagram which schematically illustrates arecycling apparatus of a First Preferred Embodiment according to thepresent invention;

FIG. 2 is a graph which illustrates a temperature characteristic and apressure characteristic along with a longitudinal axis of a cylinder ofthe recycling apparatus illustrated in FIG. 1;

FIG. 3 is a cross-sectional view of the recycling apparatus taken alongthe arrows "3"--"3" of FIG. 1;

FIG. 4 is a construction diagram which schematically illustrates arecycling apparatus of a Second Preferred Embodiment according to thepresent invention;

FIG. 5 is a construction diagram which schematically illustrates arecycling apparatus of a Third Preferred Embodiment according to thepresent invention;

FIG. 6 is a construction diagram which schematically illustrates crackproducing means of the recycling apparatus of the Third PreferredEmbodiment;

FIG. 7 is a construction diagram which schematically illustrates crackproducing means of a recycling apparatus of a Fourth PreferredEmbodiment according to the present invention;

FIG. 8 is a perspective view which illustrates a major portion of aforward-feed full-flighter employed by a recycling apparatus of a FifthPreferred Embodiment according to the present invention;

FIG. 9 is a construction diagram which schematically illustrates crackproducing means of a recycling apparatus of a Sixth Preferred Embodimentaccording to the present invention;

FIG. 10 is a construction diagram which schematically illustrates crackproducing means of a recycling apparatus of a Seventh PreferredEmbodiment according to the present invention;

FIG. 11 is a construction diagram which schematically illustrates arecycling apparatus of an Eighth Preferred Embodiment according to thepresent invention together with crack producing means thereof;

FIG. 12 is a construction diagram which schematically illustrates arecycling apparatus of a Ninth Preferred Embodiment according to thepresent invention together with washing means thereof;

FIG. 13 is a transverse cross-sectional view which schematicallyillustrates a major portion of the washing means of the Ninth PreferredEmbodiment;

FIG. 14 is a construction diagram which schematically illustrates arecycling apparatus of a Tenth Preferred Embodiment according to thepresent invention together with washing means thereof;

FIG. 15 is a construction diagram which schematically illustrates arecycling apparatus of an Eleventh Preferred Embodiment according to thepresent invention together with washing means thereof;

FIG. 16 is a transverse cross-sectional view which schematicallyillustrates a major portion of the washing means of the EleventhPreferred Embodiment;

FIG. 17 is a transverse cross-sectional view which schematicallyillustrates portions around a sealing ring employed by a recyclingapparatus of a Twelfth Preferred Embodiment according to the presentinvention;

FIG. 18 is a plan view which schematically illustrates portions aroundthe sealing ring employed by the recycling apparatus of the TwelfthPreferred Embodiment;

FIG. 19 is a cross-sectional view which schematically illustratesportions around the sealing ring employed by the recycling apparatus ofthe Twelfth Preferred Embodiment;

FIG. 20 is an enlarged cross-sectional view which schematicallyillustrates major portions of FIG. 19;

FIG. 21 is a side view which schematically illustrates portions around asealing ring employed by a recycling apparatus of a Thirteenth PreferredEmbodiment according to the present invention, and in which the upperhalf of the portions is illustrated in cross-section;

FIG. 22 is a side view which schematically illustrates portions around asealing ring employed by a recycling apparatus of a Fourteenth PreferredEmbodiment according to the present invention, and in which the upperhalf of the portions is illustrated in cross-section;

FIG. 23 is a side view which schematically illustrates portions around asealing ring employed by a recycling apparatus of a Fifteenth PreferredEmbodiment according to the present invention, and in which the upperhalf of the portions is illustrated in cross-section;

FIG. 24 is a front view which schematically illustrates a gear kneaderemployed by a recycling apparatus of a Sixteenth Preferred Embodimentaccording to the present invention, and which is viewed in the directionof the arrow "24" of FIG. 25;

FIG. 25 is a side view which schematically illustrates the gear kneaderemployed by the recycling apparatus of the Sixteenth PreferredEmbodiment; and

FIG. 26 illustrates construction diagrams of screws which can beemployed by the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Having generally described the present invention, a furtherunderstanding can be obtained by reference to the specific preferredembodiments which are provided herein for purposes of illustration onlyand are not intended to limit the scope of the appended claims.

The preferred embodiments will be hereinafter described with referenceto the accompanied drawings.

First Preferred Embodiment Recycling Apparatus and Resin Scrap

FIG. 1 schematically illustrates a recycling apparatus employed by theFirst Preferred Embodiment together with its screw arrays arrangement.FIG. 2 illustrates the temperature characteristic of resin materialemployed by the First Preferred Embodiment. FIG. 3 schematicallyillustrates a transverse cross-sectional view of the recycling apparatustaken along the arrows "3"--"3" of FIG. 1. In the First PreferredEmbodiment, a double-axis screw extrusion apparatus, e.g., Type "TEX44"made by THE JAPAN STEEL WORKS, Ltd., is employed for the recyclingapparatus. The double-axis screw extrusion apparatus is a uni-directionrotary type, and includes two screw arrays whose screw outside diameteris 44 mm, which are disposed parallelly, and which rotate in the samedirection.

The recycling apparatus comprises a cylinder 1 including a passage 1a, asupply port 2 formed at an end of the passage 1a of the cylinder 1 forsupplying resin material resulting from scrap, a discharge port 3 formedat the other end of the passage 1a of the cylinder 1 for dischargingrecycled resin composition, and a plurality of water supply ports (e.g.,a first water supply port 1k, a second water supply port 1m and a thirdwater supply port 1n) for supplying water in the passage 1a of thecylinder 1. The first, second and third water supply ports 1k, 1m and 1nare provided with a check valve 1z.

In the passage 1a of the cylinder 1, there are defined a melting region4, a hydrolysis region 5, a degassing region 6 and a kneading region 7in series in this order from the upstream side to the downstream side ofthe screw arrays constituting the present delivering means, e.g., in thedirection of the arrow U1 from the supply port 2 to the discharge port3. As illustrated in FIG. 1, there are disposed full-flighter screws(hereinafter simply referred to as "full-flighters") 50 and 52, kneadingdisks 54, 56 and 58, and so on around a driving shaft 1y in series in apredetermined combination. When the driving shaft 1y rotates, thesemembers rotate. Immediately below the supply port 2, there is disposedthe forward-feed full-flighter 50 which has a large delivery capability.

In the First Preferred Embodiment, pulverized products W_(o) areemployed as the resin material, and are made by pulverizing vehiclebumpers (i.e., resin scrap with paint film) with a pulverizer, and havea square shape in a size of about 5 mm×5 mm. In the resin scrap made upof the pulverized products W_(o), an acrylics-melamine resin pain filmis laminated on an exposed surface of a thermoplastic polypropylenesubstrate. The pulverized products W_(o) were supplied through thesupply port 2 into the passage 1a in an amount of 50 kg per hour.

In the First Preferred Embodiment, water for carrying out hydrolysis issupplied through the first, second and third water supply 1k, 1m and 1ninto the passage 1a. The water is supplied in an amount of 10 parts byweight in total with respect to 100 parts by weight of the resinmaterial. In the First Preferred Embodiment, the water is supplied in anamount more than required for hydrolyzing the resin material.Accordingly, despite the shearing heat generation action of the screwarrays, the resin material can be inhibited from excessively generatingheat. Thus, the resin material, especially the thermoplastic resinsubstrate, can be kept from degrading.

Concerning the relationship between the water supply amounts per unittime through the first, second and third water supply ports 1k, 1m and1n, it is possible to adjust as follows:

    ______________________________________                                        (the water supply amount through                                              the first water supply port 1k) >                                             (the water supply amount through                                              the second water supply port 1m) >                                            (the water supply amount through                                              the third water supply port 1n).                                              ______________________________________                                    

For example, the ratio of the water supply amounts can be determined asfollows:

    ______________________________________                                        (the water supply amount through                                              the first water supply port 1k):                                              (the water supply amount through                                              the second water supply port 1m):                                             (the water supply amount through                                              the third water supply port 1n): =                                                                      5:3:2.                                              ______________________________________                                    

Since the resin material is kneaded under high shearing stress in themelting region 4 on the upstream side, it is heated to high temperatureswhen it flows into the hydrolysis region 5. Hence, the temperature ofthe resin material should be adjusted to temperatures appropriate forhydrolysis (e.g., temperatures not causing the thermal degradation ofresin material). Further, the ratio is determined as described above inorder to inhibit the temperature of the resin material from loweringsharply, to keep it appropriate for hydrolysis, and to effectively carryout hydrolysis.

The screw arrays disposed in the aforementioned regions and theiractions will be hereinafter described in detail for each of the steps ofthe present recycling process.

Melting Step

In the First Preferred Embodiment, the screw arrays are constituted bycombining double-start thread kneading disks 54, 56 and 58 in themelting region 4 as illustrated in FIG. 1. In the melting step, theresin material is heated by the shearing friction resulting from therotation of the screw arrays and by a heater built in the cylinder 1.During the heating, the paint film deposited on the surface of the resinmaterial is pulverized mechanically into pieces by the shearing frictionresulting from the rotation of the kneading disks 54, 56 and 58, and itssurface area increases. As a result, a contact efficiency can beimproved between the paint film pieces and the water or the water vapor.The thus pulverized paint film pieces are dispersed in the molten resinmaterial, and are delivered to the downstream side, i.e., to thehydrolysis region 5.

Hydrolyzing Step

In the hydrolysis region 5 of the cylinder 1, there are disposed sealingrings 10 and 11, working as the present resistors, on the downstreamside and the upstream side, respectively, thereby enhancing the sealingproperty. Accordingly, the pressure in the hydrolysis region 5 ismaintained at high pressures, e.g., from 10 to 100 kgf/cm² . Since thepressure is kept thus high, the temperature of the resin material can bemaintained at temperatures, e.g., from 180° to 280° C., higher thanthose produced by the prior art. As a result, the hydrolysis can becarried out at higher temperatures than it is done by the prior art, thehydrolysis reaction can be facilitated and accomplished effectively, andthe hydrolysis reaction time can be reduced.

The hydrolysis region 5 includes three regions 5A, 5B and 5C. In thehydrolysis region 5A, a screw array 20 is constituted by combining aforward-feed double-start thread kneading disk 54 disposed below thefirst water supply port 1k, a reverse-feed double-start thread kneadingdisk 56 and an orthogonal double-start thread kneading disk 58.

There is also disposed a screw array 30 in the hydrolysis region 5A. Thescrew array 30 is constituted by combining a reverse-feed full-flighter52 disposed on an upstream side and a sealing ring 13 disposed on adownstream side. The sealing ring 13 constituting the screw array 30operates as the present resistor for restricting the delivery of theresin material to the downstream side. Likewise, the reverse-feedfull-flighter 52 constituting the screw array 30 has a capability ofdelivering the resin material to the upstream side, and consequentlyoperates as the present resistor. With this arrangement, the resinmaterial is likely to be packed in the space between the screw array 30and the screw array 20. Accordingly, in the space between the screwarray 30 and the screw array 20, there is formed a highly packed regionwhere a packing efficiency of the resin material is enhanced. Forinstance, it is believed that the packing efficiency would fall in arange of approximately from 70 to 100%. In particular, it is believedthat the packing efficiency would be about 30% at the forward-feedfull-flighter 50 having a large capability of delivering the resinmaterial.

With the thus formed highly packed region, the hydrolysis region 5 canbe enhanced in terms of the sealing property, and the pressure thereincan be maintained at high pressures. For example, when the resinmaterial was delivered in the amount of 50 kg per hour, the pressure was50 to 60 kgf/cm² around the first water supply port 1k in the passage1a.

Further, there are repetitively disposed the screw arrays 20 and 30,which can form a highly packed region where a packing efficiency of theresin material is enhanced, in series as illustrated in FIG. 1. In otherwords, the same screw arrays 20 and 30 are constituted by combining theidentical component members, and are similarly disposed in thehydrolysis regions 5B and 5C, respectively. Furthermore, there aredisposed forward-feed full-flighters 50 (i.e., screw arrays 40), whichhave a high delivering capability and work as the present deliveringmeans, on the upstream sides with respect to the screw arrays 20 and 30.Hence, the recycling apparatus is securely provided with an ability ofdelivering the resin material to the downstream side.

Those members, like the reverse-feed full-flighter 52, having littledelivering ability can operate so as to let the resin material reside inthe hydrolysis region 5 for an extended period of time. Therefore, theycan securely and advantageously provide the hydrolysis time.

In the First Preferred Embodiment, as can be appreciated from FIG. 1,the water is supplied through the first water supply port 1k, the secondwater supply port 1m and the third water supply port 1n into thehydrolysis region 5. The supplied water is dispersed in the molten resinmaterial by the action of the screw arrays 20 and 30. Consequently, thefine paint film pieces dispersed in the resin material contacteffectively with the liquid water or the water vapor to efficientlycause hydrolysis. The fine paint film pieces can be converted intolow-molecular-weight compounds because their molecular chains are out bythe kneading action of the screw arrays 20 and 30. Hence, the paint filmpieces from the melting region 4 can be further subdivided in thehydrolysis region 5.

When the pressure is kept at the saturation vapor pressure or more inthe hydrolysis region 5, the water is present in the resin material in aform of the liquid water and the water vapor. When the pressure ismaintained at pressures less than the saturation vapor pressure in thecylinder 1, the water heated to high temperatures is believed to existin the resin material in a form of the water vapor if there is ampletime left for the water to vaporize.

In the First Preferred Embodiment, as can be seen from FIG. 1, the wateris supplied through the first water supply port 1k into the hydrolysisregion 5A, through the second water supply port 1m into the hydrolysisregion 5B, and through the third water supply port 1n into thehydrolysis region 5C. Thus, the water supply ports are provided in thesame quantity as that of the highly packed regions. With thisarrangement, the hydrolysis can be carried out effectively, andsimultaneously the resin material can be inhibited from beingexcessively heated. In addition, the first water supply port 1k isdisposed on an upstream side of the hydrolysis region 5A, the secondwater supply port 1m is disposed on an upstream side of the hydrolysisregion 5B, and the third water supply port 1n is disposed on an upstreamside of the hydrolysis region 5C. The reasons behind this arrangementare to down-size the cylinder 1 in the longitudinal axis direction, andat the same time to securely enlarge the length of the hydrolysisregions 5A, 5B and 5C over which the hydrolysis carried out.

Degassing Step

In the degassing region 6 of the cylinder 1, the water supplied throughthe first, second and third water supply ports 1k, 1m and 1n isdischarged through a vent hole 1v to the outside of the cylinder 1. Inthe degassing step, the pressure in the cylinder 1 is virtually theatmospheric pressure because it is released to the atmosphere, and thewater is discharged as the water vapor through the vent hole 1v. Thedecomposed components of the resin material are partially dischargedtogether with the water vapor. This phenomenon can be verified byconducting an experiment in which resin material free from paint film ishydrolyzed. In the First Preferred Embodiment, the discharge wasslightly white. However, in the experiment, the discharge was colorless.

Kneading Step

In the kneading step, the temperature of the cylinder 1 is adjusted tothe melting point of the resin material or less in the kneading region7. The thus decreased temperature increases the viscosity of the reinmaterial, and accordingly enlarges the shearing force resulting from thescrew arrays. Accordingly, the paint film pieces can be subjected toenlarged mechanical cracking force, and can be converted intolow-molecular-weight compounds. Thus, the paint film pieces can befurther subdivided advantageously. In the kneading region 7, asillustrated in FIG. 1, the screw array is constituted by a forward-feedfull-flighter 50, a forward-feed double-start thread kneading disk 54, areverse-feed double-start thread kneading disk 56, an orthogonaldouble-start thread kneading disk 58 and a forward-feed full-flighter 50which are disposed in this order.

The thus produced recycled resin composition is discharged cut of a die,which is disposed in the discharge port 3 of the cylinder 1, through ascreen mesh, and formed as a shape of 4 mm-diameter rods. In order topelletize the recycled resin composition, the rods are cooled withwater, and cut to approximately 3 mm in length by a strand cutter (notshown). In accordance with the First Preferred Embodiment, the timerequired for recycling (or the residing time) was about from 2 to 3minutes. Thus, the recycling time was reduced sharply compared to thatof the prior art.

FIG. 2 schematically illustrates temperature distribution of the resinmaterial in the passage 1a of the cylinder 1 with the characteristiccurve F1. As described above, the water is supplied through the first,second and third water supply ports 1k, 1m and 1n into the passage 1a,and accordingly the temperature drops around the first, second and thirdwater supply ports 1k, 1m and 1n as illustrated by the characteristiccurve F1. The pressure in the passage 1a is illustrated by thecharacteristic curve F2. In the degassing region 6, the pressure issubstantially the atmospheric pressure because the degassing region 6communicates with the external atmosphere by way of the vent hole 1v.Basically, the term "pressure" herein means the sum of the water vaporpressure and the pressure of the resin material associated with thedelivery. Therefore, in the region where the resin material packingefficiency is low, for instance, at the forward-feed full-flighters 50having a high delivering ability, the ratio of the pressure of the resinmaterial associated with the delivery is believed to be low. On theother hand, in the region where the resin material packing efficiency ishigh, for instance, at the screw arrays 30 which include the sealingrings 11 and 13 restricting the delivery of the resin material to thedownstream side, the ratio of the pressure of resin material associatedwith the delivery is believed to be high.

Screw Configuration

Concerning the arrangements of the screws employed by theabove-described First Preferred Embodiment, for instance, the helixangle (or lead), pitch and number of starts of the screws, they can bedetermined depending on applications. FIG. 26 illustrates examples ofthe screw arrangement. FIG. 26 (A) and (B) illustrate an example of theforward-feed full-flighter 50. FIG. 26 (C) and (D) illustrate an exampleof the reverse-feed full-flighter 52. In FIG. 26 (B) and (D), though theinner wall surface of the passage 1a of the cylinder 1 is formed in acircle with substantial roundness, it is abbreviated virtually. Theforward-feed full-flighter 50 is adjusted in terms of the helicaldirection of screw 50i so as to securely produce the ability ofdelivering the resin material to the downstream side. The reverse-feedfull-flighter 52 is adjusted in terms of the helical direction of screw52i so as to decrease the ability of delivering the resin material tothe downstream side. FIG. 26 (E) and (F) illustrate an example of theorthogonal double-start thread kneading disk 58. In the orthogonaldouble-start thread kneading disk 58, there are disposed paddles 58e,having apexes 58x and formed virtually as an oval disk, at anintersecting angle of 90° in series. The orthogonal double-start threadkneading disk 58 little has the ability of delivering the resin materialbecause it is not provided with a helix angle. However, it has a highshearing ability, and accordingly has a high dispersing ability as wellas a high kneading ability. FIG. 26 (G), (H) and (I) illustrate anexample of the forward-feed double-start thread kneading disk 54. Theforward-feed double-start thread kneading disk 54 includes paddles 54ehaving apexes 54x and formed virtually as an oval disk, and the apexes54x were disposed in series in a manner slanting downward from left toright. FIG. 26 (J), (K) and (L) illustrate an example of thereverse-feed double-start thread kneading disk 56. The reverse-feeddouble-start thread kneading disk 56 includes paddles 56e having apexes56x and formed virtually as an oval disk, and the apexes 56x weredisposed in series in a manner slanting upward from left to right.

In particular, it is preferable to dispose a screw having a highdispersing ability and a high kneading ability, for instance, a kneadingdisk, immediately below the first, second and third water supply ports1k, 1m and 1n, because the kneading disk enhances the waterdispersibility and increases the contact efficiency between the resinmaterial and the water. It is especially preferable to employ areverse-feed kneading disk having a helix angle of from 30° to 150° oran orthogonal kneading disk for this purpose.

Second Preferred Embodiment

The Second Preferred Embodiment according to the present invention willbe hereinafter described with reference to FIG. 4. Basically, arecycling apparatus employed by the Second Preferred Embodiment has theidentical construction with that employed by the First PreferredEmbodiment. For example, the steps carried out in the melting region 4,the degassing region 6 and the kneading region 7 are basically identicalwith those of the First Preferred Embodiment. However, in the SecondPreferred Embodiment, the recycling apparatus employs screw arrays,which are different from those of the First Preferred Embodiment, forthe hydrolysis region 5. Therefore, the hydrolysis region 5 according tothe Second Preferred Embodiment will be hereinafter described in detail.

Hydrolysis Region 5

In the hydrolysis region 5 of the Second Preferred Embodiment, similarlyto the First Preferred Embodiment, there are also disposed the sealingrings 10 and 11 on the most upstream side and the most downstream side,respectively, thereby keeping the pressure in the hydrolysis region 5high. In FIG. 4, there are illustrated screw arrays 20. The screw arrays20 are constituted by combining the orthogonal double-start threadkneading disks 58 in series, and are characterized in that theorthogonal double-start thread kneading disks 58 are disposedimmediately below the first, second and third water supply ports 1k, 1mand 1n. In FIG. 4, there are also illustrated screw arrays 30. The screwarrays 30 are constituted, similarly to those of the First PreferredEmbodiment, by combining the reverse-feed full-flighter 52 and thesealing ring 13. With these arrangements, the resin material are packedin the screw arrays 20 and 30, thereby forming a highly packed regionwhere a packing efficiency of the resin material is enhanced. Thus, thepressure in the hydrolysis region 5 can be maintained at high pressures.For example, when the resin material was delivered in the amount of 50kg per hour, the pressure was 50 to 60 kgf/cm² around the first watersupply port 1k in the passage 1a.

Further, as can be understood from FIG. 4, there are repetitivelydisposed a plurality of screw array combinations in series from theupstream side to the downstream side. The screw array combinations areconstituted by combining the same screw arrays 20 and 30. Furthermore,there are also disposed forward-feed full-flighters 50 (i.e., screwarrays 40) having a high delivering ability between the screw arrays 20and thereby securely providing the capability of delivering the resinmaterial. The water is supplied through the first water supply port 1k,the second water supply port 1m and the third water supply port 1n intothe hydrolysis region 5. The supplied water is dispersed in the moltenresin material by the action of the screw arrays 20 and 30.Consequently, the fine paint film pieces dispersed in the resin materialcan contact effectively with the liquid water or the water vapor toefficiently cause hydrolysis. The fine paint film pieces can beconverted into low-molecular-weight compounds because their molecularchains are cut by the kneading action of the screw arrays 20 and 30.Hence, the paint films from the melting region 4 can be furthersubdivided in the hydrolysis region 5.

In the Second Preferred Embodiment, the orthogonal double-start threadkneading disks 58 are disposed immediately below the first, second andthird water supply ports 1k, 1m and 1n as illustrated in FIG. 4, thewater flowed in the passage 1a is believed to be dispersed in the moltenresin material in fine particulate states. Accordingly, the surface areaof the fine particulate liquid increases so that the contact can becarried out efficiently between the fine particulate liquid and thepaint film pieces, and that the hydrolysis reaction can be facilitated.When the pressure is maintained at pressures more than the saturationvapor pressure in the cylinder 1, it is believed that the fineparticulate water can be present in the resin material in a coexistingform of the liquid water and the water vapor.

Evaluation

The First and Second Preferred Embodiments produced highly refinedrecycled resin compositions, compared with those produced by the priorart, because the paint films were further converted into thelow-molecular-weight compounds and uniformly dispersed in the recycledresin compositions by the facilitated hydrolysis reactions. Accordingly,it is possible to produce highly refined resin composition out of resinmaterial which has not been subjected to pre-treatments.

In order to verify the advantageous effect, an embrittling temperaturetest, an impact test and a flowability test were carried out.Specifically speaking, the pellets produced by the First and SecondPreferred Embodiments were molded into test specimens with an injectionmolding machine. The test specimens were examined for their embrittlingtemperatures, Izod impact strength values and MFR values. Theembrittling temperature was measured according to ASTM D746. The Izodimpact strength value was measured according to JIS K7110. The MFR valuewas measured according to JIS K7210. Likewise, test specimens producedby the following comparative examples, i.e., Comparative Example Nos. 1and 2, were examined therefor.

In Comparative Example No. 1, the test specimens were made out of virginmaterial. In Comparative Example No. 2, the test specimens were made bya conventional batch recycling process. For instance, a cylindricalbatch recycling apparatus was used in which a stirring impeller wasdisposed and which had a vapor supply port at one end in thelongitudinal axis direction and a vapor discharge port at another endtherein. The batch recycling apparatus had a diameter of 260 mm, alength of 400 mm and a recycling capacity of 7 kg resin material. Theresin material were pulverized into pieces having a square shape in asize of about 5 mm×5 mm. In the batch recycling apparatus, thepulverized resin material pieces were placed in a packing efficiency of70% by volume. While keeping the packed state, water vapor was suppliedinto the batch recycling apparatus at a rate of 5 kg/hour to carry outhydrolysis for 1 hour at a temperature of 160° C. under a pressure of5.2 kgf/cm². However, note that this conventional 1-hour hydrolysistreatment time did not include the preheating time of 3 minutes and thecooling time of 3 minutes.

The results of the examinations for the physical properties of therecycled resin compositions produced by the First and Second PreferredEmbodiments are set forth in Table 1 below together with those for thecomparative examples, and are summarized by the relative values withrespect to those of Comparative Example No. 1 taken as 100. As can beseen from Table 1, with respect to the embrittling temperature ofComparative Example No. 1 taken as 100, Comparative Example No. 2exhibited 75 thereto, the First Preferred Embodiment exhibited 80thereto, and the Second Preferred Embodiment exhibited 98 thereto. TheSecond Preferred Embodiment exhibited an especially favorableembrittling temperature. The lower the value was, the lower the recycledresin composition exhibited an embrittling temperature.

Concerning the Izod impact strength value at 23° C., Comparative ExampleNo. 2 exhibited 96 with respect to the actually examined value forComparative Example No. 1 (For instance, let it be 100 J/m.), the FirstPreferred Embodiment exhibited 91 thereto, and the Second PreferredEmbodiment exhibited 96 thereto. Concerning the Izod impact strengthvalue at -30° C., Comparative Example No. 2 exhibited 96 with respect tothe actually examined value for Comparative Example No. 1 (For instance,let it be 100 J/m.), the First Preferred Embodiment exhibited 91thereto, and the Second Preferred Embodiment exhibited 96 thereto.

Concerning the MFR value, Comparative Example No. 2 exhibited 111 withrespect to the actually examined value for Comparative Example No. 1(For instance, let it be 100 g/10 min.), the First Preferred Embodimentexhibited 106 thereto, and the Second Preferred Embodiment exhibited 100thereto.

                  TABLE 1                                                         ______________________________________                                               1st Pref.                                                                              2nd Pref.  Comp.    Comp.                                            Embodiment                                                                             Embodiment Ex. No. 1                                                                              Ex. No. 2                                 ______________________________________                                        Recycled 50         50         --      7                                      Amount                                                                        (kg/hr.)                                                                      Water    10         10         --     71                                      Addition                                                                      Amount                                                                        (PHR)                                                                         Recycling                                                                               5          5         --     60                                      Time                                                                          (min.)                                                                        Embrittling                                                                            80         98         100    75                                      Temp.*                                                                        Izod Impact                                                                            91         96         100    96                                      Strength                                                                      at 23° C.*                                                             Izod Impact                                                                            92         97         100    74                                      Strength                                                                      at -30° C.*                                                            MFR Value*                                                                             106        100        100    111                                     ______________________________________                                         (Note)                                                                        The values marked with * are the relative values with respect to those of     Comparative Example No. 1 (i.e., virgin material).                       

Third Preferred Embodiment

The Third Preferred Embodiment according to the present invention willbe hereinafter described with reference to FIGS. 5 and 6. Basically, arecycling apparatus employed by the Third Preferred Embodiment has theidentical construction with that employed by the First PreferredEmbodiment. As illustrated in FIG. 5, however, in the Third PreferredEmbodiment, the recycling apparatus is provided with crack producingmeans 60 on an upstream side with respect to the melting region 4.

The crack producing means 60 includes a box-shaped base 60b providedwith a hopper 60a, a first roller 61 disposed in the base 60b and heldrotatably therein, and a second roller 62 held rotatably in the base 60band facing the first roller 61. As illustrated in FIG. 6, on an outerperipheral portion of the first roller 61, there are formed a pluralityof first projections 61x in a zigzag arrangement. Likewise, on an outerperipheral portion of the second roller 62, there are formed a pluralityof second projections 62x in a zigzag arrangement. FIG. 6 illustratespart of the first and second projections 61x and 62x.

The first and second projections 61x and 62x can be formed as a squarecone, a triangular cone, or a circular cone. The first and secondprojections 61x and 62x can be rotated at the same speed or differentspeeds each other. Let the thickness of the pulverized products W_(o) bet_(o) before being charged into the hopper 60a, the height H1 of thesecond projections 62x can be adjusted to (1 to 3) t_(o), and thepitches of the zigzag arrangement of the second projections 62x can alsobe adjusted to (1 to 3) t_(o). The first projections 61x can be adjustedsimilarly. The clearance B1 between the convexity and concavity of thefirst and second rollers 61 and 62 can be adjusted to (0.2 to 0.8)t_(o).

In the supplying process, when the first roller 61 is rotated in thedirection of the arrow X1, the second roller 62 is rotated in thedirection of the arrow X2 and the resin scrap of about 5 mm×5 mm squarepieces is pulverized and charged into the hopper 60a, the pulverizedresin scrap pieces are compressed and extended by the first and secondrollers 61 and 62. Since the thermosetting resin paint film is lesslikely to extend than the thermoplastic resin substrate, the cracks arelikely to be produced in the paint film. The cracks are thus produced inthe paint film, and accordingly the paint can be pulverized into furtherfine pieces and its surface area can be enlarged. As a result, the paintfilm can be furthermore fined in the melting region 4, and, in thehydrolysis region 5, the hydrolyzing agent and the paint film can becontacted at an enhanced efficiency. Further, in the hydrolysis region5, the hydrolyzing agent can penetrate into the cracks. Thus, the ThirdPreferred Embodiment can contribute to facilitating the hydrolysisreaction, reducing the recycling time and producing highly refinedrecycled resin composition.

Fourth Preferred Embodiment

The Fourth Preferred Embodiment according to the present invention willbe hereinafter described with reference to FIG. 7. Basically, arecycling apparatus employed by the Fourth Preferred Embodiment has theidentical construction with that employed by the Third PreferredEmbodiment. However, in the Fourth Preferred Embodiment, the recyclingapparatus is provided with multideck crack producing means 65. The crackproducing means 65 includes a box-shaped base 60b provided with a hopper60a, a first roller 61 and a second roller 62 which are disposedrotatably on an upper portion of the base 60b and which face each other,and a third roller 63 and a fourth roller 64 which are disposedrotatably on a lower portion of the base 60b and which face each other.Similarly to the first projections 61x, there are formed a plurality ofthird projections 63x in a zigzag arrangement on an outer peripheralportion of the third roller 63. Similarly to the second projections 62x,there are formed a plurality of fourth projections 62x in a zigzagarrangement on an outer peripheral portion of the fourth roller 64. Thethird and fourth projections 63x and 64x can be formed as a square cone,a triangular cone, or a circular cone.

The clearance S1 between the upper-side first and second rollers 61 and62 are adjusted so as to be larger than the clearance S2 between thelower-side third and fourth rollers 63 and 64. For instance, theclearance S1 can be adjusted to (0.2 to 0.8) t_(o), and the clearance S2can be adjusted to (0.1 to 0.5) t_(o). The first roller 61 can berotated at a speed faster than the speed of the second roller 62. Forexample, the first roller 61 can be rotated at a speed of from 200 to300 rpm, and the second roller 62 can be rotated at a speed of from 100to 200 rpm. The fourth roller 64 can be rotated at a speed faster thanthe speed of the third roller 63. For example, the fourth roller 64 canbe rotated at a speed of from 200 to 300 rpm, and the third roller 63can be rotated at a speed of from 100 to 200 rpm.

When the resin scrap of about 5 mm×5 mm square pieces is charged intothe hopper 60a, the pulverized resin scrap pieces are compressed andextended by the first, second, third and fourth rollers 61, 62, 63 and64. In the Fourth Preferred Embodiment, the cracks are more likely to beproduced. The reasons behind this advantageous effect are believed asfollows. Since the speed of the first roller 61 is adjusted to be higherthan that of the second roller 62, there arises a relative speeddifference, the cracks are likely to be produced in the paint filmfacing the first roller 61 on the upper side, and the cracks are likelyto be produced in the paint film facing the fourth roller 64 on thelower side.

Moreover, in the Fourth Preferred Embodiment, the crack producing means65 is equipped with an air duct 66 which holds a filter 66t therein andwhich is disposed between the base 60b and the cylinder 1. By suctioningthrough the air duct 66 or by blowing therethrough, fine paint filmpieces, which are separated from the substrate during the pulverizingand the production of cracks, can be transferred through the filter 66talong the air duct 66 in the direction of the arrow R1, and consequentlythey can be removed.

Fifth Preferred Embodiment

In the above-described Third and Fourth Preferred Embodiments, thecracks are produced in the paint film by the crack producing means 50and 65 which are disposed outside the cylinder 1. However, the presentinvention is not limited thereto. The cracks can be produced in thepaint film within the cylinder 1. For instance, as the Fifth PreferredEmbodiment according to the present invention illustrated in FIG. 8,grooves 50s are formed in the screw of the forward-feed full-flighter50. Consequently, the wall surface of the cylinder 1 and theforward-feed full-flighter 50 can apply the shearing deformation to theunmelted resin material, thereby producing the cracks in the paint film.Note that such grooves can be formed in the screw of the reverse-feedfull-flighter 52.

Alternatively, there can be formed a large clearance between the apexesof the kneading disk 54, 56 and 58 and the inner wall surface of thecylinder 1. The unmelted resin material can be forcibly deliveredthrough the clearance, thereby producing cracks in the paint film.

Sixth Preferred Embodiment

Alternatively, as the Sixth Preferred Embodiment according to thepresent invention illustrated in FIG. 9, a plurality of grooves 1r canbe formed in the inner wall surface of the cylinder 1. The unmeltedresin material can be hooked at the grooves 1r, and the shearing forcecan be applied to the paint film by using the grooves 1r. Thus, thecracks can be produced in the paint film.

Seventh Preferred Embodiment

Alternatively, as the Seventh Preferred Embodiment according to thepresent invention illustrated in FIG. 10, a plurality of dimpled holes1s can be formed in the inner wall surface of the cylinder 1. Theunmelted resin material can be hooked at the dimpled holes 1s to applythe shearing force to the paint film by using the dimpled holes 1s.Thus, the cracks can be produced in the paint film.

Eighth Preferred Embodiment

Alternatively, as the Eighth Preferred Embodiment according to thepresent invention illustrated in FIG. 11, the cylinder 1 can be providedwith slotting means 69 which can vibrate in the direction of the arrowE. The shearing force can be applied to the paint film by vibrating theslotting means 69, thereby producing the cracks in the paint film.

Ninth Preferred Embodiment

FIGS. 12 and 13 illustrate the Ninth Preferred Embodiment according tothe present invention. In the Ninth Preferred Embodiment, there isdisposed an auxiliary cylinder apparatus 70 perpendicularly on anupstream side with respect to the cylinder 1. The auxiliary apparatus 70includes an auxiliary cylinder 70a disposed under the bottom portion ofthe cylinder 1, an auxiliary screw 70b disposed in the auxiliarycylinder 70a and rotated by a driving motor. Further, there is disposedwashing means 72 horizontally on an upstream side with respect to theauxiliary cylinder apparatus 70. The washing means 72 includes a washingcylinder 72a communicating with the auxiliary cylinder 70a and having asupply port 2, a driving shaft 72b disposed in the washing cylinder 72aand rotated by a driving motor, a screw 72c installed to the drivingshaft 72b, stirring impellets 72d and 72e installed to the driving shaft72b, washing water inlet holes 72f and 72g, washing water outlet holes72h and 72i, and a filter 72k. The filter 72k preferably has a mesh sizewhich does not allow the resin material to pass therethrough.

The foreign materials, such as mud, wax, tar and sand, are usuallydeposited on the resin scrap. In order to remove the foreign materials,in the Ninth Preferred Embodiment, the washing water is introduced intothe washing cylinder 72a through the washing water inlet holes 72f and72g, and simultaneously the driving shaft 72b is rotated. Accordingly,the resin scrap is stirred and washed by the rotary action of thestirring impellets 72d and 72e. Among the foreign materials thus washedand removed, the mud and sand having a large specific weight aretransferred through the filter 72k in the direction of the arrow F1 andevacuated to the outside. The waste water containing the foreignmaterials having a small specific weight, e.g., the wax and tar, isevacuated to the outside through the water outlet holes 72h and 72i. Inthe Ninth Preferred Embodiment, it is preferred that the level of thewashing water is adjusted to be from about 1/3 to 1/2 of the height ofthe washing cylinder 72a. Taking the washing efficiency intoconsideration, it is preferred that the packing efficiency of the resinmaterial and the washing water is adjusted to be from about 1/3 to 1/2of the accommodatable capacity of the washing cylinder 72a. The stirringimpellets 72d and 72e have a different radial length each other, and aretwisted in order to securely provide themselves an ability of deliveringthe resin material to the downstream side.

The melting region 4 is heated. Accordingly, when the washing water istransferred to the melting region 4 in a large amount, the washing watervaporizes and increases the pressure in the melting region 4. Thus, thedelivery of the resin material might be troubled. In order to removethis adverse effect, in the Ninth Preferred Embodiment, the auxiliarycylinder 70a is connected at the top end to the bottom portion of thecylinder 1. Consequently, the washing water can be inhibited from goinginto the melting region 4, and the excessive pressure increment can beavoided in the melting region 4.

Tenth Preferred Embodiment

FIG. 14 illustrates the Tenth Preferred Embodiment according to thepresent invention. Basically, a recycling apparatus employed by theTenth Preferred Embodiment has the identical construction with thatemployed by the Ninth Preferred Embodiment, and operates and producesthe advantageous effects similarly thereto. However, in the TenthPreferred Embodiment, the washing means 72 is a vertical one, and afilter 72k is installed to an outlet hole 72h which is formed at abottom of a letter U-shaped washing cylinder 72a.

Eleventh Preferred Embodiment

FIGS. 15 and 16 illustrate the Eleventh Preferred Embodiment accordingto the present invention. In the Eleventh Preferred Embodiment, washingmeans 73 includes stirring impellets 73d and 73e. The washing water isevacuated to the outside by way of a screen 74r and an outlet port 74s.Part of the washing water is delivered to the melting region 4, and isvaporized to increase the pressure therein. Hence, in order not todisturb the charging of the pulverized products W_(o) through the supplyport 2, a rotary valve 74m having a sealing ability and a deliveringability is disposed below the supply port 2, thereby making the supplyof the pulverized products W_(o) easier. A check valve 74n helps stablysupply the washing water. In addition, in the Eleventh PreferredEmbodiment, in order to inhibit the washing water from going into themelting region 4, the cylinder 1 is inclined upward from left to rightin the drawing at an angle Θ1 (e.g., from 3 to 7 degrees) with respectto the imaginary horizontal line H5 so that the discharge port 3 of thecylinder 1 faces upward.

Twelfth Preferred Embodiment

The Twelfth Preferred Embodiment according to the present invention willbe hereinafter described with reference to FIGS. 17 through 20. Asillustrated in FIG. 17, in the passage 1a of the double-axis cylinder 1,there are disposed sealing rings 80 and 83 operating as the presentresistor. The sealing rings 80 and 83 are rotated by driving shafts 1yconnected to a driving motor. Virtually on all over the outer peripheralportion of the sealing ring 80, there are formed a plurality of grooves800 and grooves 801 which face each other and are lined up in thecircumferential direction. As can be understood from FIGS. 19 and 20,there are formed expanded portions 80r at the boundary between thegrooves 800 and the grooves 801 so as not to communicate the grooves 800and the grooves 801 in the axial direction. A water supply port 85 isformed so as to be capable of facing the grooves 800 of the sealing ring80. Therefore, as can be appreciated from FIG. 17, when the sealing ring80 is rotated in the circumferential direction, the water supply port 85first faces one of the grooves 800, and faces one of outer peripheralportions 800f between the grooves 800, and then faces the next one ofthe grooves 800. This operation is carried out repeatedly. When thewater supply port 85 faces the grooves 800, the hydrolyzing agent issupplied to the passage 1a through the water supply port 85. When thewater supply port 85 faces the outer peripheral portions 800f, thehydrolyzing agent supplied through the water supply port 85 is shut offor it is restricted considerably. Therefore, the hydrolyzing agentsupplied continuously through the water supply port 85 is subdivided.For instance, it is dispersed as fine bubbles. Consequently, the contactefficiency can be improved between the hydrolyzing agent and the resinmaterial, and the hydrolysis reaction can be facilitated.

In the Twelfth Preferred Embodiment, as illustrated in FIGS. 19 and 20,the hydrolyzing agent is received by the grooves 800 whose opening 800cfaces the upstream side M1, and accordingly it is likely to flow to theupstream side M1. On the other hand, the resin material flows from theupstream side M1 to the downstream side M2 in the direction of the arrowU1. Thus, the flow direction of the hydrolyzing agent is opposite tothat of the resin material, and is likely to be a turbulent flow. As aresult, the contact efficiency can be improved between the hydrolyzingagent and the resin material, and the hydrolysis reaction can befacilitated. When the facilitated hydrolysis reaction can be thusexpected, it is possible to highly refine the recycled resincomposition. Further, since it is also possible to reduce the length ofthe hydrolysis region 5, the axial length of the cylinder 1 can bereduced and accordingly the whole recycling apparatus can be down-sizedadvantageously.

Thirteenth Preferred Embodiment

In the Thirteenth Preferred Embodiment illustrated in FIG. 21, there isformed a ring-shaped groove 803 continuously in the circumferentialdirection in the outer peripheral portion of the sealing ring 80. Anopening 803c of the ring-shaped groove 803 is positioned on an upstreamside M1, and accordingly the hydrolyzing agent is likely to flow to theupstream side M1 as described above. Thus, the flow direction of thehydrolyzing agent is opposite to that of the resin material, andconsequently the hydrolyzing agent and the resin material are likely tocollide with each other like a turbulent flow. As a result, the contactefficiency can be improved between the hydrolyzing agent and the resinmaterial, and the hydrolysis reaction can be facilitated.

Fourteenth Preferred Embodiment

In the Fourteenth Preferred Embodiment illustrated in FIG. 22, there areformed a plurality of minor holes 805, facing the water supply port 85,in the outer peripheral portion of the sealing ring 80. The minor holes805 have an opening 805c which faces an upstream side M1, andaccordingly the hydrolyzing agent is likely to flow to the upstream sideM1. Thus, the flow direction of the hydrolyzing agent is opposite tothat of the resin material, and is likely to be a turbulent flow. As aresult, the contact efficiency can be improved between the hydrolyzingagent and the resin material, and the hydrolysis reaction can befacilitated.

Fifteenth Preferred Embodiment

FIG. 23 illustrates the Fifteenth Preferred Embodiment according to thepresent invention. In the Fifteenth Preferred Embodiment, there areformed a plurality of grooves 807 lined up in the circumferentialdirection in the outer peripheral portion. The water supply port 85 isformed at a position where it can face the grooves 807 formed in theouter peripheral portion of the sealing ring 80. The sealing ring 80rotates, and, as aforementioned, finely subdivides the hydrolyzing agentwhich is supplied continuously through the water supply port 85. As aresult, the hydrolysis reaction can be facilitated. Note that, in theFifteenth Preferred Embodiment, an opening 807c of the grooves 807,receiving the hydrolyzing agent, faces a downstream side M2.

Sixteenth Preferred Embodiment

In the above-described preferred embodiments, the kneading disks areemployed to constitute the screw arrays. However, a gear kneader cansubstitute the kneading disks to constitute the screw arrays. Namely, inthe Sixteenth Preferred Embodiment according to the present inventionillustrated in FIGS. 24 and 25, a gear kneader 90 substitutesaforementioned kneading disks to constitute the screw arrays. In FIG.24, the gear kneader 90 is viewed in the direction of the arrow "24" ofFIG. 25 (i.e., in the resin material delivery direction). The gearkneader 90 includes a first rotor 92 provided with a plurality of gearteeth 91 on the outer peripheral portion, and a second rotor 94 providedwith a plurality of gear teeth 93 on the outer peripheral portion. Asillustrated in FIG. 25, between the gear teeth 91 of the first rotor 92neighboring in the longitudinal axis direction, there are disposed thegear teeth 93 of the second rotor 94.

The first gear teeth 91 include an apex 91b having a predetermined helixangle (or lead), opposing surfaces 91c and 91d with the apex 91binterposed therebetween and facing each other with their rear surfaces,connecting surfaces 91e, and cylindrical outer peripheral surfaces 91f.When the apexes 91b are interconnected in the longitudinal axisdirection, there arises a lead T as defined by the imaginary line ofFIG. 25. The first rotor 92 rotates in the direction of the arrow ofFIG. 25, and accordingly the ability of delivering the resin material inthe direction of the arrow "24" of FIG. 25 can be securely produced bythe helix angle of the opposing surfaces 91d.

The second rotor 94 has basically the same construction as that of thefirst rotor 91, and accordingly the second gear teeth 93 of the secondrotor 94 have basically the same construction as that of the first gearteeth 91 of the first rotor 92.

There are formed clearances 95 between the first gear teeth 91 and thesecond gear teeth 93. The clearances 95 are formed as a letter "U" shapeor an inverted letter "U" shape, and are disposed continuously in thedirection of the arrow "24" of FIG. 25 (i.e., in the resin materialdelivery direction), thereby securely producing a kneading capabilityand a dispersing capability. Moreover, it is preferable to dispose thegear kneader 90 immediately below the first, second and third watersupply ports 1k, 1m and 1n, because this arrangement can advantageouslyimprove the efficiency of the hydrolysis.

In addition, note that the clearances 95 of the gear kneader 90 are sosmall that they increase the resistance against the delivery of theresin material. Thus, the gear kneader 90 can also operate as thepresent resistor which restricts the delivery of the resin material.Therefore, it is preferable to dispose the gear kneader 90 at positionsin the hydrolysis region 5 where the highly packed region is formed.

Modified Versions

The present recycling process and apparatus are not limited to thepreferred embodiments described above and illustrated in the drawings,but can be accomplished by appropriately modifying them depending onrequirements. For example, it is possible to effectively determine,depending on applications, the screw arrays disposed in the passage 1aof the cylinder 1, the helix angle, the pitch, the L/D, and the numberof the screws and paddles. Further, in the aforementioned preferredembodiments, the present recycling process and apparatus are applied tothe double-axis screw extrusion apparatus. However, they can be appliednot only thereto, but also to a single-axis screw extrusion apparatusand the other multi-axis extrusion apparatus, such as a triple-axis orquadruple-axis screw extrusion apparatus.

Having now fully described the present invention, it will be apparent toone of ordinary skill in the art that many changes and modifications canbe made thereto without departing from the spirit or scope of thepresent invention as set forth herein including the appended claims.

What is claimed is:
 1. A process for recyclingscrap resin materialcomprising a hydrolyzable thermosetting resin and a thermoplastic resinas its major components in apparatus having an upstream side and adownstream side and comprising a cylinder including a passage extendingfrom the upstream side to the downstream side, at least part of thepassage defining a hydrolysis region, and means for delivering the resinmaterial from the upstream side to the downstream side, the deliveringmeans being disposed in the passage and including resistor meansdisposed therein so as to restrict the delivery of the resin material tothe downstream side in the hydrolysis region to form a highly packedregion where a packing efficiency of the resin material is enhanced onan upstream side of the resistor means, which process comprises thesteps of: introducing the resin scrap, into the upstream side of thepassage; melting the thermoplastic resin of the resin material whiledelivering the introduced resin material from the upstream side to thedownstream side; introducing into the hydrolysis region a hydrolyzingagent effective to hydrolyze the thermosetting resin and hydrolyzing thethermosetting resin by contacting the resin material containing meltedthermoplastic resin with the hydrolyzing agent; resulting from thethermosetting resin; restricting the delivery of the resin material tothe downstream side in the hydrolysis region so as to improve a contactefficiency between the resin material and the hydrolyzing agent in thehydrolyzing step; and vaporizing water resulting from the hydrolysis ofthe thermosetting resin.
 2. The process according to claim 1, whereinsaid resin material is hydrolyzed under a pressure of from 10 to 100kgf/cm² at a temperature of the resin material from 180° to 280° C. 3.The processing according to claim 1, wherein said resistor meansincludes a plurality of resistors disposed in series at predeterminedintervals in said passage, and said cylinder includes a plurality ofsupply ports, each disposed on an upstream side of one of saidresistors, for supplying said hydrolyzing agent to said passage, andsaid hydrolyzing agent is supplied to said passage through each of thesupply ports.
 4. The process according to claim 3, wherein saidhydrolyzing agent is supplied in a larger amount to said passage throughsaid supply ports which are disposed on the upstream side of the passagethan through said supply ports which are disposed on the downstream sideof the passage.
 5. The process according to claim 4, the plurality ofsupply ports comprises a first supply port, a second supply port and athird supply port, the supply ports being disposed in series in thisorder from the upstream side to the downstream side of said passage, andsaid hydrolyzing agent is supplied in a larger amount to said passagethrough the first supply port than through the second supply port, andit is supplied in a larger amount to said passage through the secondsupply port than through the third supply port.
 6. The process accordingclaim 1, wherein said hydrolyzing agent is water, and the water is addedto the passage in an amount of from 5 to 40 parts by weight with respectto 100 parts by weight of said resin material.
 7. The process accordingto claim 1, wherein longitudinally axial ends of said hydrolysis regionare defined by said resistor means.
 8. The process according to claim 1,wherein said hydrolysis region is constituted by, at least, a firsthydrolysis region, a second hydrolysis region and a third hydrolysisregion which are disposed in series from the upstream side to thedownstream side.
 9. The process according to claim 8, wherein saidfirst, second and third hydrolysis regions are defined by anupstream-side resistor, disposed on an upstream side thereof, and adownstream-side resistor, disposed on a downstream side thereof.
 10. Theprocess according to claim 1, wherein said resistor means is constitutedby at least one sealing ring which substantially covers a flow passagearea of said passage and which restricts the delivery of said resinmaterial, and at least one reverse-feed full-flighter which is disposedadjacent to and on an upstream side with respect to the sealing ring.11. The process according to claim 1, wherein said thermoplastic resinis at least one member selected from the group consisting ofpolypropylene, polypropylene modified with elastomer, polyethylene, ABSresin, AS resin, polyamide resin, polyester resin, polycarbonate resinand polyacetal resin, and said thermosetting resin is a paint filmcomprising at least one member selected from the group consisting ofacrylics-melamine resin, alkyd-melamine resin and polyurethane resin.